This invention relates to a photosensitive resin composition and a photosensitive resin composition laminate (hereinafter abbreviated as "photosensitive film") and more particularly it relates to a photosensitive resin composition and a photosensitive film which are excellent in resistance to plating and stability.
Photosensitive resin compositions and photosensitive films have been widely used as resist materials for etching, plating, etc., for example, in production of printed circuit boards and precision machining of metals. As a process for producing a printed circuit board, plating method is becoming a leading process because in recent years, the pattern density of printed circuit board has been increased and the width of pattern has been reduced.
The plating method comprises coating a resist on a substrate except for portions in which through-holes for mounting chips and an electric circuit are to be formed, forming the through-holes and the electric circuit, peeling off the resist, followed by etching, and thereby obtaining the electric circuit. As a plating solution in the plating method, there are used solutions of copper pyrophosphate, copper sulfate, solder, nickel, palladium, gold, etc. In general, copper sulfate is used for producing an electric circuit and solder is used for protecting the electric circuit.
In the plating method, an additive is incorporated into a photosensitive resin composition in order to enhance the adhesion between a base metal (copper is mainly used) and a photosensitive film. As the additive, there have been disclosed a heterocyclic compound in Japanese Patent Appln. Kokai (Laid-Open) No. 53-702, phthalazone or a derivative thereof in Japanese Patent Appln. Kokai (Laid-Open) No. 55-65202, indazole or a derivative thereof in Japanese Patent Appln. Kokai (Laid-Open) No. 55-65203, tetrazole or a derivative thereof in Japanese Patent Appln. Kokai (Laid-Open) No. 59-125726, lophine in Japanese Patent Appln. Kokai (Laid-Open) No. 59-125727, and carboxybenzotriazole in Japanese Patent Appln. Kokai (Laid-Open) No. 63-24243.
However, employment of these compounds improves the adhesion but causes the following troubles. After development, organic substances tend to remain on a base metal (resulting in reddening of the base metal surface when the remaining is not considerable, or resulting in a phenomenon called "scum"), and no plating layer is deposited, or the adhesion between deposited metal and the base metal is lowered, so that a plating layer is peeled off.
Japanese Patent Appln. Kokai (Laid-Open) No. 61-223836 has disclosed a 1,2,3-benzotriazole derivative. Employment of this compound is disadvantageous in that when there is conducted gold plating, copper plating using copper pyrophosphate, or the like, which requires severe treatment conditions, there is caused peeling-off of a resist film, its lifting, or underplating of a plating layer (a phenomenon that a plating layer is deposited under a resist and on a substrate metal surface).
In the production of a printed circuit board, there are many steps from lamination of a photosensitive film on a base metal to formation of a resist pattern, and therefore a long time is often required (in particular, the lamination product is often allowed to stand for 1 to 14 days from the lamination to imagewise exposure), so that the above-mentioned reddening and scum are promoted. Conventional photosensitive resin compositions have a low heat stability and hence undergo thermopolymerization, resulting in reddening or scum. For suppressing the thermopolymerization, additives are often used in photosensitive resin compositions. As the additives usable for this purpose, there are well known and often used quinones such as hydroquinone, benzoquinone, hydroquinone monomethyl ether, etc., and phenolic compounds. But, employment of such an additive causes problems such as lowering of the sensitivity and increase of the exposure time. From such a viewpoint, when the additive is used, its amount is preferably 1 part by weight or less, more preferably 0.5 part by weight or less, most preferably 0.1 part by weight or less, per 100 parts by weight of a polymerizable vinyl compound.